1. Field of the Invention
The present invention relates to an image capturing module, in which an image capturing element having a plurality of light receiving sections for performing photoelectric conversions on and capturing image light from a subject and a lens for forming an image of incident light on the image capturing element are modularized (integrated); a method for manufacturing the image capturing module; and an electronic information device, such as a digital camera (e.g., digital video camera and digital still camera), an image input camera (e.g., car-mounted camera), a scanner, a facsimile machine, a camera-equipped cell phone device, and a personal digital assistant (PDA), having the image capturing module as an image input device (e.g., car-mounted camera) used in an image capturing section thereof.
2. Description of the Related Art
A conventional image capturing module of this type is mainly used for a camera-equipped cell phone device, a personal digital assistant (PDA), and further a card camera. In such an image capturing module, a solid-state image capturing chip, which includes a plurality of light receiving sections for performing photoelectric conversions on and capturing image light from a subject, and a holder member fixing a lens for forming an image of incident light on the image capturing element are provided on a substrate of ceramics, epoxy resin with glass in it, and the like. In this case, it is important to accurately fix a distance between the lens and the image capturing element and accurately form an image of incident light on the image capturing element in order to obtain a clear image.
Reference 1 discloses a way to directly contact and fix a bottom surface of a lens tube for fixing a lens on the periphery of an image capturing element on a solid-state image capturing chip, as a method for accurately defining the distance between the lens and the image capturing element. First, the image capturing module of Reference 1 will be described in detail with reference to FIG. 8.
FIG. 8 is a structural diagram schematically illustrating an exemplary essential structure of a conventional image capturing module disclosed in Reference 1. FIG. 8(a) is a longitudinal cross sectional view of the conventional image capturing module, and FIG. 8(b) is a top view of the conventional image capturing module.
In FIG. 8, a conventional image capturing module 100 includes a lens section 101 and an image sensor chip 102. Herein, the lens section 101 is configured of a lens 101a and a lens tube 101b for fixing the lens 101a. In addition, the image sensor chip 102 includes a sensor section 102a as an image capturing element, a logic circuit section 102b for processing a signal from the sensor section 102a, and a bonding pad 102c as an input and output terminal for connecting the logic circuit section 102b and the outside.
The lens 101a is an aspherical convex lens herein, and has a function for forming an image of incident light on a surface of the image sensor chip 102.
The lens tube 101b has a shape of a cylinder, a square shape and the like, and supports the lens 101a at a predetermined position in its internal circumference portion. The lens tube 101b functions as a lens supporting section. The lens supporting section is not required to be formed into a tube shape. For example, the lens supporting section may support the lens 101a with a single or multiple points from the bottom. The bottom surface of the lens tube 101b is fixed on the logic circuit section 102b of the image sensor chip 102 at a space d where no sensor cover 102d is provided. In this example, the sensor cover 102d is equipped with coupling sections e extending in four directions, and four lower end sections of the lens tube 101b are mounted and fixed on the image sensor chip 102 at the four spaces d without the coupling sections e.
The lens tube 101b and the image sensor chip 102 are adhered to each other by ultraviolet curable resin, for example. In this case, the bottom surface of the lower end portion of the lens tube 101b is placed on a predetermined position of the image sensor chip 102, and subsequently, ultraviolet curable resin is applied so as to adhere the image sensor chip 102 to the lens tube 101b. Alternately, the image sensor chip 102 and the lens tube 101b may be positioned after ultraviolet curable resin is applied to either or both of the image sensor chip 102 and the lens tube 101b. Ultraviolet rays are radiated on the ultraviolet curable resin so as to adhere and fix the image sensor chip 102 and the lens tube 101b. Thus, according to the conventional camera module 100, the lens supporting section (lens tube 101b) for supporting the lens 101a is placed on the image sensor chip 102 to be directly fixed, thereby achieving a reduction in size. Since the lens supporting section (lens tube 101b) is the only member between the lens 101a and the image sensor chip 102, the error due to stacking is small for the distance between the lens 101a and the sensor section 102a of the image sensor chip 102, and therefore, the relative positions of the lens and image sensor chip can be set with a high accuracy and be placed more securely.
The sensor section 102a of the image sensor chip 102 is formed on a center surface of the image sensor chip 102, and is an image capturing element for converting optical information into an electric signal and outputs the electric signal as an image capturing signal. The image capturing element includes a great number of readout pixels. The sensor section 102a is a CCD element and a CMOS element, for example. In the sensor section 102a, a plurality of microchip lenses are formed above the readout pixels, the microchip lenses being capable of focusing incident light on the readout pixels.
The logic circuit section 102b performs a variety of signal processing, such as amplifying process and a noise reduction process, for an image capturing signal outputted from each sensor section 102a. 
The bonding pad 102c is an input and output terminal electrically connected to the logic circuit section 102b. The bonding pad 102c is electrically connected to an outer electrode by wire bonding. For example, the image sensor chip 102 is positioned on a circuit board that configures a circuit of a cell phone device, a personal digital assistant (PDA), a card camera and the like, and the bonding pad 102c and the circuit board are electrically connected by wire bonding. Further, the image sensor chip 102 is positioned on a sub circuit board, on which a passive part, such as a resistor and a capacitor, and an active part, such as a transistor and an LSI, are mounted; and the bonding pad 102c and the sub circuit board are electrically connected by wire bonding. The sub circuit board can also be electrically connected to a cell phone device, a personal digital assistant (PDA), a card camera and the like.
The sensor cover 102d is positioned for protecting at least the sensor section 102a, preventing a foreign object from adhering to the sensor section 102a. The sensor cover 102d has a contact section, which is fixed to the image sensor chip 102 outside the area of the sensor section 102a. A space is formed between the sensor cover 102d and the sensor section 102a. The sensor cover 102d is formed of a synthetic resin or glass, which is transparent. The synthetic resin includes various types of resin, such as silicon resin, polycarbonate resin, styrene resin, acrylic resin, nylon resin and the like. The sensor cover 102d is adhered or crimped onto the image sensor chip 102. When adhered, ultraviolet curable resin, for example, is used. The sensor cover 102d is formed at a manufacturing stage of an image capturing module, and is continued to be attached during the usage stage of the image capturing module. That is, the sensor cover 102d is not removed at the usage stage. Therefore, the sensor cover 102d above the sensor section 102a is required to be transparent in order to allow incident light to pass. However, the entire sensor cover 102d is not required to be transparent.
The distance between an incident surface of the sensor cover 102d, namely the surface on the lens 101a side, and the surface of the sensor section 102a is required to be greater than or equal to a predetermined distance. Incident light that has passed the lens 101a gradually converges and an image is formed on the sensor section 102a. Therefore, a foreign object would appear in a different size in an image captured by the sensor section 102a in a case where the foreign object adhered directly to the sensor section 102a and in a case where the foreign object adhered to the sensor cover 102d, which is away from the sensor section 102a upwards by a predetermined distance. Specifically, in a case where the lens 101a is a converging lens, the farther the incident surface of the sensor cover 102d becomes separated upwards from the sensor section 102a, the smaller the foreign object adhering to the sensor cover 102d is shown on an image of the sensor section 102a. Therefore, the influence of the adhesion of the foreign object can be reduced.
The sensor cover 102d has a connecting section for connecting to the sensor cover 102d of an adjacent image sensor chip 102, as illustrated in FIG. 8(b). The connecting section is cut off at the time of dicing. All the chips on a wafer are formed as one body by the connection section connecting with the sensor cover 102d. 
In addition, in order to maintain the optical accuracy, the sensor cover 102d is not provided at a contacting part of the lens tube 101b and the image sensor chip 102 such that the lens tube 101b and the image sensor chip 102 directly contact with each other. Instead, an opening (spaced) of the sensor 102d is provided. Similarly, in order to facilitate the wiring, the sensor cover 102d is not provided above the bonding pad 102c, and instead, the opening of the sensor cover 102d is provided.
According to Reference 1 as described above, the four bottom surfaces of the lower end portion of the lens tube 101b, to which the lens 101a is fixed, are placed and fixed to the image sensor chip 102, so that the distance is accurately defined between the lens 101a and the sensor section 102a. Further, according to Reference 1, additional values, such as an “IR cut filter”, a “diaphragm” and a “low pass filter”, are added to the sensor cover 102d itself, and four through holes (spaces d through which legs extending from the bottom surface of the lens tube 101b pass) are provided to the sensor cover 102d. Further, legs extend from the bottom surface of the lens tube 101b and directly touch the image sensor chip 102, so that the distance is accurately defined between the lens 101a and the sensor section 102a. 
Next, an image capturing module according to Reference 2 will be described in detail with reference to FIG. 9. In Reference 1, the lens tube 101b intervenes between the lens 101a and the sensor section 102a. On the other hand, Reference 2 discloses a way to accurately define the distance between a lens and an image capturing element by extending a portion of a lens part for a focal distance (distance to a sensor) and press the tip portion extending from the lens part to a chip image sensor.
FIG. 9 is a longitudinal cross sectional view schematically illustrating an exemplary essential structure of a conventional image capturing apparatus disclosed in Reference 2.
In FIG. 9, a conventional image capturing apparatus 200 includes: a substrate 201; an image capturing element 202 positioned on one surface of the substrate 201; an optical member 203 for focusing light and forming an image of a subject in an image capturing area of the image capturing element 202; a lens frame (holder member) 204 for covering the optical member 203 and the image capturing element 202; a rotating member 205 provided on an upper surface (front portion) of the lens frame 204 and equipped with a magnet; a light shielding plate 206 provided below the rotating member 205 and for shielding light; an aperture plate 207 provided below the light shielding plate 206 and for adjusting the amount of light entering the optical member 203; an IR cut filter 208 supported by the shielding plate 206 and the aperture plate 207; a pressing member 209 that is a spring that presses the optical member 203 towards the substrate 201 side and is provided inbetween the aperture plate 207 and the optical member 203; and a position-determining electric part 210 for determining a position of the lens frame 204. The rotating member 205, the shielding plate 206, the aperture plate 207 and the IR cut filter 208 are defined as an upper end portion 211 (front portion of the holder member) of the lens frame 204.
Transparent glass or plastic material is used for the optical member 203, and the optical member 203 is configured of a first lens member 212 positioned on the substrate 201 side (back of an optical axis direction), a second lens member 213 provided above the first lens member 212, an aperture portion 214 provided in between the first lens member 212 and the second lens member 213 and for adjusting the amount of light entering the first lens member 212. The optical axes of the first lens member 212 and the second lens member 213 are identical to each other.
The first lens member 212 includes a convex shaped first lens portion 212a and a tubular lower leg portion 212b around the first lens portion 212a. In a normal image capturing mode, a touching portion 212c is formed for touching a surface of the image capturing element 202 at a lower end portion of the lower leg portion 212b. In addition, the pressing member 209 touches an upper surface of the lower leg portion 212b. In a normal image capturing mode, the first lens member 212 is pressed to the substrate 201 side by the pressing force (bias force) of the pressing member 209. Further, a collar portion 212d is formed in a circular shape in a plan view from the tubular lower leg portion 212b towards the outside. Although the focal distance of the first lens member 212 is a distance from the principal point of the lens, in terms of parts measurement, the distance and measure from a flat surface position of the collar portion 212d to the touching portion 212c at a lower end of the lower leg portion 212b are controlled by manufacturing the tolerance.
As a result, part of the first lens member 212 is extended to the position of the focal distance (distance to a sensor) and a tip portion (touching portion 212c at the lower end) of the lower leg portion 212b extending from a lower surface of the first lens member 212, is pressed to the surface of the image capturing element 202. The first lens member 212 and the image capturing element 202 can be positioned so that the distance can be set in a highly accurate manner between the first lens member 212 and the image capturing element 202.
Next, Reference 3 discloses a camera module, in which an image capturing element chip is positioned on a substrate and a tubular holder having a lens therein covering the image capturing element chip. In order to determine the distance between the lens and the image capturing element chip, a lower surface of a protruding portion protruding from the holder is adhered to a surface of the image capturing element chip via adhesive.
Reference 4 discloses a method for manufacturing the camera module according to Reference 3. In this case, a projection portion of the holder is drawn near to the upper surface of the image capturing element chip via adhesive while checking the focusing state of the lens. Subsequently, the position of the holder is determined at the position where the lens is focused on the image capturing element and the adhesive is dried.
Further, Reference 5 discloses a camera module, the camera module including an image capturing chip being positioned on a substrate, a ceiling surface portion positioned on the image capturing element chip, a protrusion portion protruding from the ceiling surface portion to the image capturing element chip side, where the upper surface of the image capturing element chip and the ceiling surface portion are fixed via adhesive in a state where the protrusion portion is touching the upper surface of the image capturing element chip.
Reference 1: Japanese Laid-Open Publication No. 2004-260356
Reference 2: Japanese Laid-Open Publication No. 2004-266340
Reference 3: Japanese Laid-Open Publication No. 2007-184801
Reference 4: Japanese Laid-Open Publication No. 2007-150428
Reference 5: Japanese Laid-Open Publication No. 2007-259064